The present invention is directed, in general, to dual-swiping interconnection clip, and hook and slot arrangement for printed circuit board (PCB) attachment.
U.S. Pat. No. 5,691,504 (xe2x80x9cthe ""504 patentxe2x80x9d), issued Nov. 25, 1997, to Sands et alii and assigned to Dell USA, L.P., provides an excellent background with respect to the present invention, and relevant background discussions have been liberally used from such patent.
While the present invention will be described with respect to a chassis and PCB in a computing apparatus environment (e.g., a personal computer (PC) or server), practice of the present invention is not limited thereto.
A chassis for a computing apparatus has many functions. As one function, it serves as a mounting structure to which the components are secured in prescribed relative positions to one another to allow convenient interconnecting of the components. One such component is a PCB. Background methods of securing a PCB (e.g., a motherboard) to a chassis of the computing apparatus are not only labor intensive, but have disadvantages arrangements.
More particularly, with regard to manufacturing, a plurality of hooks may be stamped in a floor of the chassis and bent upward in a subsequent bending step. The hooks are arranged to provide structure for mating with slots in the PCB and allowing sliding between the PCB slot and mated hook, with the hook ultimately capturing opposing sides of the PCB. The hooks may be, by themselves, inadequate to provide sufficient grounding of the PCB to the chassis, since the contact area between the hooks and the PCB is relatively small and since variations in PCB thickness negate any guarantee of a tight conduction fit with the hooks to form a good grounding path.
Accordingly, some background chassis further provide a plurality of bosses that rise from the chassis floor at predetermined locations and provide a grounding path between the PCB and the chassis. Such bosses are adapted to receive screws or bolts that pass through holes in the PCB. Once the PCB is slid into a desired position within the channel created by the hooks, significant labor is required to align the apertures of the PCB with respect to the bosses and to drive the individual screws or bolts through each of the holes into their corresponding bosses. Further disadvantageously, the bosses are often thread-stripped during manufacture or repair when the screws or bolts are over-torqued or axially misaligned. Still further, the screws may dangerously fall into the equipment, thus representing a short-circuiting agent.
Other background chassis (e.g., the ""504 patent) use spring members that rise from the chassis floor at predetermined locations and provide a grounding path between the PCB and the chassis. Such spring members are stamped in, and monolithic with, a floor of the chassis and then bent upward in a subsequent bending step.
As a disadvantage, the locations of the bosses and stamped hooks/spring-members are often chosen primarily to afford the most reliable mechanical support for the PCB, as well as to insure continued rigidity of the chassis, i.e., they are rarely optimized for electrical grounding. Such places a burden on the designer to take care in the design of the PCB to route grounding traces to the correct locations on the PCB. Such often results in awkward and inefficient PCB layout.
In another chassis function, the chassis serves as a barrier for electromagnetic interference (xe2x80x9cEMIxe2x80x9d) caused by electromagnetic fields generated inside or outside the chassis. As computers have grown more powerful, the electronic components thereof have become faster, increasing the potential for generation of interfering (and thus often illegal) radio frequency interference (xe2x80x9cRFIxe2x80x9d). Further, the electronic components have themselves become more sensitive to RFI generated externally. Therefore, good chassis design dictates that open holes in the chassis be minimized to block EMI. Further, the chassis should provide a grounding path for energy contained in the EMI. Since the hooks and background spring members are formed by stamping and bending a portion of the floor of the chassis, each resulting hook and background spring member has associated therewith a punched aperture in the chassis created by the displacement of material to create the hook or spring member. Such is disadvantageous in allowing EMI to leak into and out of the chassis.